The present invention relates to a method for fabricating automotive interior components such as automotive door trims, rear corner trims and other components related to the upholstery and other ornamental members used in the passenger compartment of the motor vehicle.
A conventional automotive interior component, for instance the automotive door trim 1 illustrated in FIG. 8, typically comprises a resin core member 2 molded into a desired curved shape, and a surface skin member 3 laminated on the outer surface of the resin core member 2. Normally, to the end of simplifying the process of fabrication, the surface skin member 3 is attached to the resin core member 2 at the same time as molding the resin core member 2.
As illustrated in FIG. 9, a mold press die assembly having a lower die 4 and an upper die 5 is opened, and the surface skin member 3 is held between the lower die 4 and the upper die 5 of the mold press die assembly by clamping the periphery of the surface skin member 3 with a clamping device 6. Then, the upper die 5 is lowered until a predetermined clearance or a cavity is defined between the upper and the lower dies 4 and 5, and resin material 8 consisting of polyolefin resin material in semi-molten state is introduced into this cavity from gates provided in the lower die 4. Thereby, the surface skin member 3 is integrally attached to the surface of the resin core member 2 at the same time as the resin material 8 is molded into a resin core member 2 having a desired curved shape as illustrated in FIG. 10.
However, according to such a conventional method for fabricating automotive interior components, in case the upper and lower dies 4 and 5 of the mold press die assembly have complicated die surface contours, since the peripheral part of the surface skin member 3 is engaged by corner edges 4a and 5a of the upper and lower dies 4 and 5, the surface skin member 3 may not be able to conform to the curved surface contour of the dies 4 and 5, causing breakage to highly stretched portions of the surface skin member 3 in extreme cases.
Further, when the semi-molten resin material 8 flows into the cavity defined between the upper and lower dies, the surface skin member 3 causes an added resistance to the flow of the resin material 8, and the clearance between the upper and lower dies 4 and 5 must be increased accordingly. This not only increases the consumption of the material, but also increases the thickness of the resin core member 2 thereby undesirably increasing the weight of the fabricated component. Also, the added resistance to the flow of the resin material requires the use of a sufficiently fluid resin material, and this restricts the choice of the resin material.
In view of such problems of the prior art, a primary object of the present invention is to provide a method for fabricating an automotive interior component integrally combining a resin core member and a surface skin member without involving breakage of the surface skin member even when the shape of the component is highly complicated.
A second object of the present invention is to provide a method for fabricating an automotive interior component integrally combining a resin core member and a surface skin member which can reduce the weight of the fabricated component and save the material cost through improvement of the flow property of the resin material.
These and other objects of the present invention can be accomplished by providing a method for fabricating an automotive interior component comprising a resin core member having a desired shape, and a surface skin member attached to an external surface of the resin core member, comprising the steps of: giving a required shape to the surface skin member by using a die assembly for mold press forming while a peripheral part of the surface skin member is secured by a clamping device; opening a die assembly for mold press forming and placing the surface skin member in a cavity defined in the die assembly; supplying resin material in semi-molten state into the cavity; and engaging the die assembly having the surface skin member placed therein to mold the resin material into the resin core member having a desired shape and integrally attach the surface skin member to the molded resin core member.
Since the surface skin member is formed into an approximately final shape by a preliminary forming process, the surface skin member is not subjected to any excessive tension when the resin core member is mold press formed in its semi-molten state in the subsequent step, and the breakage and wrinkling of the surface skin member can be positively avoided.
Furthermore, since the surface member presents very little resistance to the flow of the resin material, the thickness of the product can be reduced as desired. Also, the reduced flow resistance broadens the choice of the material for the resin core member and the number of the gates in the die assembly can be reduced. The reduction in the number of gates in the die assembly contributes to the reduction in the cost of the die assembly.
Preferably, the surface skin member is softened by heat in the step of giving a required shape to the surface skin member so that the surface skin member may be shaped into a desired shape without creating any undue residual stress therein. To the end of simplifying the process of fabrication, the die assembly for giving a required shape to the surface skin member may be the same die assembly in which the resin core member is molded with the surface skin member placed therein.
Such a method can be conveniently carried out with a die assembly for fabricating an automotive interior component consisting of a resin core member having a desired shape and a surface skin member laminated on an outer surface of the resin core member, comprising: a lower die having a required die surface; an extruder associated with the lower die so as to supply resin material for molding the resin core member onto the die surface of the lower die; an upper die having a die surface defining a cavity required for molding the resin core member in cooperation with the die surface of the lower die; power means for moving the upper die toward and away from the lower die; and an annular clamping device provided on the upper die for securing a peripheral part of the surface skin member which is held between the die surfaces of the upper and lower dies.